Utilizing renewable resources such as co-products from grain processing to produce a C5-platform of biochemical and biofuels is advantageous from the perspective of the environment, process integration and economics, as well as energy independence and national security. Those co-products are richer in hemicelluloses and the C5 sugars derived from those co-products can be converted via chemical synthesis routes to higher-value bio-jet fuels and high energy density components of bio-jet fuels.
Hemicellulose-based sugars (e.g., xylose and arabinose) can be a platform for synthesis of a variety of industrially important chemicals that are currently derived from petroleum. Pentoses were identified by the U.S. Department of Energy in 2004 among the top candidates of valuable chemical precursors that could be produced from biomass. While numerous studies have been performed to develop processes for extraction of monosaccharides from a wide range of biomass feedstocks, these monosaccharide extraction processes have been developed as pretreatment processes to improve the downstream processes—not necessarily to isolate and use pentose sugars from the biomass feedstocks. For example, various hydrolytic techniques, such as steam explosion, steam explosion with dilute sulfuric acid, organosolv extraction, and biological treatment with white rot fungi, have all been extensively investigated as pretreatment methods to obtain hydrolyzates rich in monosaccharides.
However, the sugar concentrations in the resulting hydrolyzates are typically still lower than desired for downstream processing. As such, hydrolyzate concentration is often required before conversion to value-added chemicals or biofuels. These concentration steps may deteriorate the sugars and many of the sugar degradation compounds are toxic to the fermentation process, severely limiting yields and effectiveness of the overall processes. To address these drawbacks, one hydrolyzate treatment approach relies upon lipophilic boronic acids to form boronate complexes with cis-diol moieties of sugars, which are extracted into an organic phase by ion pairing with lipophilic quaternary ammonium cations. The resulting salts are then hydrolyzed in a clean, aqueous acidic solution to regenerate the sugars for use in subsequent fermentation or other enzymatic processes. Although this approach extracts sugars from the hydrolyzate, the utility of the extracted sugars is limited, as the aqueous sugar solution is not compatible with many biofuel or biochemical conversion schemes that require the sugars to be in dry form.
Accordingly, there remains a need in the art for a process of isolating C5 sugars, such as xylose, from hydrolyzates in a manner that allows the C5 sugars to then be converted and/or used in the production of a C5-platform of biochemical and biofuels.